1. Field of the Invention
The invention relates generally to stand-off insulators. The invention relates specifically to porcelain stand-off insulators having depressions therein where stud means are secured to the porcelain body of the insulator with an intermediate babbit or similar material.
2. Description of the Prior Art
It is known to dispose stud members in openings in insulating members by utilizing an intermediate flowable material which subsequently hardens. Examples of this are found in the following U.S. Pat. Nos.: 3,054,851, issued Sept. 18, 1962 to F. C. Foxe et al, entitled "Electrical Suspension Insulator With Improved Pin;" 1,594,207, issued July 27, 1962, to W. D. Kyle, entitled "Insulator;" and 1,022,993, issued Apr. 9, 1912 to G. W. Willis, also entitled "Insulator." It is also known to dispose a stud or pin in an insulator where the head of the pin or stud member is enlarged for the purpose of securing the pin or stud member to the insulator. Examples of this can be found in the following U.S. Pat. Nos.: 2,304,204, issued Dec. 8, 1942, to B. B. Ratzman, entitled "Electrical Insulator;" 1,735,982, issued Nov. 19, 1929, to C. R. Short, entitled "Resilient Connector;" 774,001, issued Nov. 1, 1904 to L. Steinberger, entitled "Track Structure"; 936,370, issued Oct. 12, 1909, to F. L. Sessions, entitled "Hanger For Wires"; 1,793,430, issued Feb. 17, 1931, to W. S. Mayer, entitled, "Bus Support"; 3,402,218, issued Oct. 1, 1968, to P. B. Thompson, entitled, "Weldable High Voltage Terminal"; 1,794,780, issued Mar. 3, 1931, to A. H. Leipert, entitled, "Spring Suspension"; and 2,279,170, issued Apr. 7, 1942 to S. B. Kraut, entitled, "Insulated Support For Lighting Units." It is also known to utilize female studs having wide shoulder portions in insulators such as is shown in U.S. Pat. No. 876,828, issued Jan. 14, 1908 to B. C. McNutt, entitled, "Insulator." Finally, it is also known to provide a stud or support member for utilization in conjunction with a cooperating insulator where the support member is free to move within the insulator, such as is disclosed in U.S. Pat. No. 2,396,131, issued Mar. 5, 1946 to W. M. Scott, Jr., entitled, "Bus Bar Support." All of the above U.S. patents present certain problems which render them less useful in many applications than the present invention. As an example, those members which utilize a widened head portion for the stud often require intricate assembly technique and in many instances introduce strain against the insulator member which may cause the member to break under certain conditions of utilization. Those members which utilize a stud and insulator in conjunction with an intermediate cement-like material either are not adapted in many cases to have a threaded end or when a threaded end is provided, the torquing of a fastening means on that threaded end may cause the stud to pull away from the cement-like material. In some circumstances the fastening or torquing operation may appear at first to be successful only to later deteriorate because of mechanical or physical relaxation or yielding of the intermediate cement-like material. This is especially true over long periods of time or when the insulator is exposed to significant variations in temperature. Those members which utilize the female insert require a matching bolt for securing purposes. In many applications, the utilization of a bolt is not desired or even possible because of space limitations. It would be advantageous if an insulator assembly could be provided having a stud means thereon for fastening purposes where the stud means could be utilized in conjunction with a separate fastening means such as a correspondingly threaded nut for securing and/or supporting electrical apparatus such as a bus bar or a bus bar supporting assembly. It would be advantageous if the bus bar and/or bus bar assembly could be disposed in place on the insulator in such a manner that a specific torque could be applied and then maintained over a relatively long period of time and over a relatively wide range of temperature variation. It is often necessary to maintain a predetermined value of torque in a fastening apparatus or assembly within reasonable limits. If, as an example, the applied torque is too large, insulator fracturing or radial shearing of the head from the intermediate cement-like material may occur. On the other hand, if the applied torque is too small, vibration and electrical forces may tend to cause the bus bar or bus bar assembly to loosen over a period of time. This is especially true where parallel bus bars or current carrying conductors are exposed to electrical conditions which cause magnetic interaction among the bus bars, which in turn cause forces to be applied at the point where a bus bar assembly is joined to an insulator.